Under the survey, "middle class" is defined as those who earn between 50 percent below and 100 percent above a country’s average household income. About two-thirds of the middle class own a home, according to the survey.

About half of middle-class consumers will take a vacation in the next year. They also tend to gravitate to high-tech devices and lifestyles, with about half owning a tablet computer and one-third watching TV via the Internet.

The expected uptick in spending will be driven largely by emerging markets, as consumer sentiment in many developed nations weakened by financial crises and economic uncertainty, said the report.  

Consumer spending in developed countries grew by only 2.6 percent annually from 2007 and 2012, said the report.

By comparison, consumer spending in emerging markets grew by 10.4 percent annually from 2008 to 2013. That was partly driven by “explosive growth” in the size of the middle class in emerging economies.

The middle class covered by the survey is well-educated, with about two-thirds holding a bachelor’s degree. Still, almost a third say tackling personal debt is a top financial priority.

In the United States, consumer sentiment rose to its highest and most positive level in six years, in the latest University of Michigan/Thomson Reuters survey. Strong consumer appetite is expected to grow more slowly in late 2013 and 2014, however.

The online survey polled 6,600 people from 16 countries.